[alwillis]

It's probably a 5:2 fast—five days of intermittent fasting and two days of 500-600 calories [1].

On the fasting days, it could be 16 hours of fasting and an 8-hour feeding window (16:8 in the fasting lingo).

[1]: https://www.healthline.com/nutrition/the-5-2-diet-guide

[Johnny555]

If they are doing intermittent fasting, then why do they have to "reintroduce" foods during the 10 day feeding window, when they've been eating food every day?

[foxyv]

These are probably foods that weren't allowed during the eating windows.